Why, why, why do we say “so long!!” as a farewell??
According the the handy-dandy Oxford English Dictionary, it dates from 1865 in English and looks to be an Anglicization of the German so lange, which means something like “that’s enough” or “that’s all.”
This site http://phrases.shu.ac.uk/bulletin_board/3/messages/616.html dismisses the idea that it is from Arabic “salaam” or Hebrew “shalom” and suggests that it is just a conventional abbreviation for some such expression as ‘Don’t let it be so long until we meet again’.
I have heard it suggested - I have no authority and no cite - that it is an anglicisation of “slán”, a Gaelic expression used as a farewell. It’s pronounced something like “slawn”.
I know german pretty well, and have lived there for about a year, in various parts of the country, and I’m pretty sure so lange doesn’t mean “thats enough” or “thats all”. But then again, in 1865, maybe!
Sorry, you’re quite right. I lost a bit in c&p.
Read that as “Which I assume meant something like ‘that’s that’.”